Carbon dioxide-hydrate product and method of manufacture thereof

ABSTRACT

A method for preparing a frozen carbonated beverage that remains stable at home freezer temperatures as well as commercial freezer temperatures, and a frozen carbonated beverage produced by said method. According to a preferred method of the invention, carbon dioxide-hydrate is prepared, ground, and mixed with a frozen flavored syrup component. The resulting mixture is compacted and packaged for storage and shipping.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a frozen carbonated product, andmore particularly to a frozen CO₂-hydrate food product, such as a frozencarbonated beverage, and method of making the same.

[0002] Various methods of preparing effervescent ice confectionproducts, such as CO₂-hydrate-containing confections are well known.See, for example, U.S. Pat. No. 4,738,862. In general, these techniquesinvolve contacting water with CO₂ under pressure and reducing thetemperature until a solid CO₂-water clathrate, also termed CO₂-hydrate,is formed. The hydrate is then ground, producing particles of the frozenCO₂-hydrate, which can then be mixed with a flavored confection phase,followed by freezing the resulting mixture.

[0003] One of the problems with prior art methods of producingCO₂-hydrate products is that insufficient carbonation is achieved. Thisresults in a frozen product that, while adequate from the standpoint ofsweetness and flavor, lacks sufficient carbonation to produce the feelin the mouth consumers associate with carbonated liquid beverages.

[0004] Other shortcomings of the prior art include relatively longreaction times being required for preparation of the CO₂-hydrate, andminimal throughput, with the result that until now there has been nocommercially viable process available for the production of aCO₂-hydrate ice confection product.

[0005] Yet another problem with the prior art is the instability of theCO₂-hydrate, which loses carbonation rapidly during the first 24 hoursafter formation. To slow the rate of loss of carbonation, it is oftennecessary to maintain the hydrate under severe temperature or pressureconditions that are not commercially feasible for the home user market,wherein home freezers operate at atmospheric pressure and around −10 to+5° Fahrenheit.

[0006] Another drawback with prior art processes is that they do notreadily lend themselves to preparation of a diet product. Diet productshave no sugar, and do not behave the same as sugar-containing productsupon freezing. Until now, there has been no commercial process availablefor producing an artificially sweetened CO₂-hydrate product.

[0007] Still another drawback with prior art methods of producingCO₂-hydrate products is the tendency of such products to “explode” or“pop,” i.e., disintegrate unpredictably with a loud noise, particularlywhen immersed in liquid. One possible explanation for this is theformation of dry ice during the carbon dioxide hydration process.

[0008] Accordingly, an improvement in the art could be realized if acarbon dioxide-hydrate product could be developed that addressed some orall of the aforementioned shortcomings.

SUMMARY OF THE INVENTION

[0009] The present invention provides a method for manufacturing afrozen carbonated confection product that exhibits high CO₂ retentionwithout significant dry ice formation and stable storage in the homefreezer environment. As used herein, the term “stable” is intended tomean that the frozen carbonated confection product can be stored attypical home freezer temperatures for typical storage durations withoutlosing significant amounts of CO₂. According to a preferred method ofpracticing the invention, water at ambient pressure is charged to areactor and subjected to an inert gas purge, preferably using CO₂, tominimize air entrainment in the resulting frozen product. Airentrainment can result in lower CO₂ retention levels. After the purge,the water is chilled to just above the freezing point, preferably to32.1° F. The chilled water is agitated, and carbon dioxide underpressure, preferably about 400 psig, is introduced into the reactorwhere the CO₂-hydrate reaction is allowed to proceed with continuedagitation for about thirty minutes. The reaction mixture is then cooledto about −5° F., resulting in a solid CO₂-hydrate containing product,which is then ground to an acceptable particle size. Preferablyfollowing grinding, or alternatively prior to or during grinding of theCO₂-hydrate product, a flavored syrup is mixed with the CO₂-hydrateproduct, and the resulting product is dispensed, preferablyincorporating a compacting step, for packaging and storage.

[0010] These and other advantages and preferred embodiments of theinvention will become more readily apparent as the following detaileddescription of the preferred embodiments proceeds, particularly withreference to the appended drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0011] The present invention will be more fully understood from thedetailed description below when read in connection with the accompanyingdrawing wherein like reference numerals refer to like elements andwherein:

[0012]FIG. 1 is a schematic flow chart of a preferred method ofpracticing the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] Clathrates are compounds comprising two types of molecules, whereone type of molecule, known as the guest molecule, occupies a cavitywhich is found in the crystal lattice structure of another type ofmolecule. In one specific type of clathrate known as a clathratehydrate, the guest molecule occupies cavities in the crystal latticestructure of water. One particular type of hydrate of interest is carbondioxide hydrate, a compound in which carbon dioxide molecules reside ina cage-shaped structure enclosed by a plurality of water molecules. Alsoreferred to herein as CO₂-hydrate, and represented theoretically by theformula [CO₂.(5.75)H₂O], clathrate CO₂-hydrates form when carbon dioxidegas is combined with water at a predetermined pressure and temperature.Although subject to various phase changes depending on the pressure andtemperature, for present purposes, the CO₂-hydrates are solid, ice-likecompositions that form according to an exothermic reaction as follows:

CO₂(gas)+H₂O(liquid)→CO₂.H2O(solid)+Δheat

[0014] The theoretical ratio of CO₂ to H₂O in CO₂-hydrate is 1:5.75. TheH₂O molecule lattice structure, however, comprises two small cavitiesand six large cavities, each of which may be occupied by a molecule ofCO₂. Thus, the number of CO₂ molecules enclosed in this lattice may varyfrom 1 to 8, depending on the specific temperature and pressureconditions under which the hydrates are formed. In general, increasingthe pressure under which hydrate formation occurs increases the numberof CO₂ molecules that become “trapped” in the ice lattice structure, or,possibly, joined by a loose chemical bond. Also, in general, increasingthe number of trapped or bonded CO₂ molecules increases the ultimate CO₂retention of a resulting frozen confection product incorporating theCO₂-hydrate.

[0015] Referring now to FIG. 1, according to a highly preferredembodiment of the present invention, water, preferably purified anddistilled, is charged to a pressure reactor 10 at ambient temperature.Purified/distilled water is preferred to minimize the inclusion of saltsand other impurities in the water, which can be detrimental to theCO₂-hydrate reaction and/or the resulting carbonation level and/orproduct shelf life. The reactor may be any suitable reactor equippedwith an agitator, such as a stirrer or shaking device, and capable ofmaintaining the pressure and temperature described herein. After beingcharged to the reactor, the water is then preferably subjected to a gaspurge, using, for example, a CO₂ purge. This purge evacuates air fromthe headspace of the reactor and thereby minimizes air entrainment inthe water during agitation. Air entrainment reduces the CO₂ retentionlevels of the resulting product. Other gasses than CO₂ can be used forthe purge, provided the purge gas is inert, such as nitrogen, however,CO₂ is the preferred purge gas for the present invention. The purge gasmay be introduced at any suitable pressure, including atmosphericpressure or under higher pressures. Most preferably, a slight positivepressure is used for the purge gas relative to the head space pressureof the reactor in order to better purge the head space of the residentair or other gas contained therein. While it is preferred to perform thegas purge after charging water to the reactor, it would also be possibleto purge the reactor of air using an inert gas prior to charging thereactor with water. Alternatively, rather than using an inert purge gas,the reactor can be evacuated of air by drawing a vacuum either before orafter being charged with water.

[0016] Following the purge step, the purged water is then subjected toan agitation phase, 11. During this phase, the water is chilled to nearfreezing, i.e., greater than 32° F. and less than or equal to about32.2° F., with agitation. Most preferably, the water is chilled to about32.1° F. The agitation helps increase surface interactions for formationof CO₂-hydrate, and also provides a uniform chill temperature, mostpreferably 32.1° F. at the outset of the CO₂-hydrate reaction. It hasbeen found that the 32.1° F. temperature of the reactants at the outsetof the CO₂-hydrate reaction is critical to achieving the superiorresults of the present invention relative to the prior art.

[0017] Agitation is also an important aspect of a highly preferredembodiment of practicing the present invention. The agitator may, forexample, be any standard implement for providing rotational mixing, suchas a paddle, or may be a shaker or other agitation mechanism, such as anultrasonic device. Any form of agitation can be used, provided that itprovides sufficient mixing to promote the CO₂-hydrate reaction, and thatit permits adequate mixing of the reactants at the outset of thereaction to achieve a uniform temperature, preferably 32.1° F., but thatdoes not impart so much energy to the reactants as to raise thetemperature of the reactants beyond the preferred range. In a preferredembodiment of the invention, where the agitator comprises a paddle, thepaddle includes a slightly curved top portion to provide verticalmixing.

[0018] Once the water is chilled to the desired temperature, CO₂ underpressure, preferably 300-500 psig, and most preferably about 400 psig,is charged to the reactor, preferably while the water continues to beagitated, although agitation is not required while the CO₂ is beingcharged to the reactor. The reaction is allowed to proceed withagitation for about 5-60 minutes, and preferably for about 30 minutes,during which time the temperature of the reactants rises to about32.2-45° F. due to the exothermic nature of the reaction. Agitation hasbeen found to be critical to achieving high CO₂ levels in the resultingCO₂-hydrate. Following the reaction, the agitation is discontinued andthe agitator is preferably lifted out of the reactants to avoid becomingfrozen therein. The reactants are chilled to subfreezing, preferablyabout −5° F. or less. During this phase, the solid CO₂-hydrate isstabilized. The finished CO₂-hydrate preferably achieves CO₂ content ofup to about 12% wt/wt CO₂ gas.

[0019] Following the freezing step, the reactor is depressurized,preferably without exposing the system to the atmosphere, althoughexposing to atmosphere can alternatively be done. When the system is notto be exposed to atmosphere, this is accomplished by maintaining aclosed system, wherein the system is depressurized by bleeding CO₂ fromthe reactor, such that the CO₂-hydrate remains under an atmosphere ofCO₂, but at or near atmospheric pressure. Alternatively, the pressure inthe system can be reduced, without completely depressurizing the systemto atmospheric pressure, for example, maintaining a slight positivepressure of around 5 psig. Of course, the reactor can also bedepressurized and then immediately exposed to the atmosphere.

[0020] After depressurization, the solid CO₂-hydrate is ground, eitherin the closed system or exposed to atmosphere, until it achieves aconsistency of fine powder, which aids in mixing. Preferably, thegrinding step is accomplished at a temperature, e.g., −5° F., thatprecludes significant melting of the CO₂-hydrate. In a preferredembodiment of the invention, the agitator is fitted with knife bladesthat permit the same mechanism used for providing agitation to also beused to grind the frozen CO₂-hydrate product.

[0021] In a highly preferred embodiment of the invention, after thegrinding step, a flavored syrup or concentrate is added to the groundCO₂-hydrate and mixed therewith. Preferably, the syrup is introduced ina chilled form, at a temperature of about −5° F. At such temperatures,the syrup assumes the consistency of a semi-solid, such as ice cream atsimilar temperatures, or may be sufficiently solid as to requiregrinding prior to mixing. The mixing is accomplished with sufficientshear to provide adequate blending of the syrup with the CO₂-hydrate,but not so much as to liquefy the components or release significantamounts of CO₂. When completed, the resulting mixture has a uniformcolor and the consistency of a loosely packed solid, like brown sugar.The mixing step may be accomplished in the closed system or after thesystem has been opened to the atmosphere. As the following examplesdemonstrate, it is also possible to add the flavored syrup componentimmediately after formation of the CO₂-hydrate, but prior to thegrinding step (Example 3). For sugar-containing syrups, it is preferrednot to add the syrup prior to completion of the CO₂-hydrate reaction, asthe presence of sugar-containing syrup tends to make the reaction lessstable, as the syrup tends to foam. It is, however, possible to addsugar-containing syrups at more than one step in the process after theCO₂-hydrate reaction is complete. On the other hand, when anartificially-sweetened syrup, such as diet Coke® syrup is used, it hasbeen found, surprisingly, that such syrup behaves like water, in that itdoes not foam excessively when added prior to the CO2-hydrate reaction,and can thus be added prior to the CO₂-hydrate reaction. For dietsyrups, therefore, it is possible to add the syrup at any step and morethan one step in the process, provided that care is taken not to removeflavor volatiles during the initial purge step.

[0022] Following mixing, the resulting product is preferably permittedto degas, to prevent swelling of the packaging. This step may beaccomplished by permitting the finished product to degas for a 24-hourperiod at a temperature of about −5° C., or could be achieved byallowing the CO₂-hydrate to degas prior to mixing with the syrupcomponent.

[0023] After the degassing step, the ground CO₂-hydrate product ispreferably subjected to a compacting step, wherein the product iscompressed into a shape convenient for consumer use, such as an ice popon a stick or in a container, such as a paper or plastic cup, box, orbowl. Such compression may be achieved using known methods. It isbelieved that compression may increase the shelf life of the CO₂-hydrateproduct. Compression is not used, however, when another preferredembodiment of the invention is prepared, wherein the product ispermitted to achieve the consistency of ice cream and is frozen incontainers without compaction. In this embodiment, the ice creamconsistency is achieved by imparting sufficient mixing and/or addingsufficient syrup to allow the mixture to achieve the smooth, creamyconsistency normally associated with an ice cream or sherbet product.When an ice cream version of the product is prepared according to thepresent invention, because there is no compaction, it is preferred thatthe product be stored at slightly colder temperatures, e.g., 0° F. orlower.

[0024] The syrup used in practicing the present invention may, forexample, be of the type commercially available from The Coca-ColaCompany, Atlanta, Ga., and used by customers at fountain outlets afterbeing mixed with carbonated water provided by the customer. In a highlypreferred embodiment of the invention, the syrup is a diet formulation,such as diet Coke®. Particularly when diet syrup is used, it has beenfound that better results are achieved by incorporating an emulsifier,such as pectin or guar gum into the product during mixing, to preventseparation.

[0025] The finished product is then packaged, for example, with asuitable wrapper and boxed for storage and shipping. Of course, theproduct is maintained at sub-freezing temperatures throughout this step.It has been found that products produced according to the presentinvention exhibit improved shelf life and can be stored at temperaturestypical of household freezers, generally about −10° F. to about 5° F. Ofcourse, the product of the present invention can be stored at coldertemperatures than home freezer temperatures, such as those temperaturestypical of commercial freezer distribution channels. As will now beapparent, the preferred method of the present invention can be carriedout as a batch or continuous process. A batch process, however, is morehighly preferred.

EXAMPLES Example 1

[0026] 1.8 grams of pectin and 0.18 grams of guar gum were dissolved in970 grams of distilled water at 120° F. The solution was cooled to roomtemperature and to it 529 grams of diet Coke® syrup was added. Theliquid was hydrated with CO₂ at 400 psig according to the proceduresdescribed herein. The product was like dry sand. The carbonation levelof the product was between 10.5 and 11.2% by weight.

Example 2

[0027] 5.15 grams of pectin and 0.515 grams of guar gum were dissolvedin 1,125 grams of water at 120° F. The solution was cooled to roomtemperature. To it 472.5 grams of diet Coke® syrup was added. The liquidwas then hydrated according to the above procedures. The product wasfrozen solid with no visible separation of the syrup. Carbonation levelof the product in this example was between 6.7 and 8.1% by weight.

Example 3

[0028] 900 grams of distilled water was placed in a 2L reactor. A CO₂hydration reaction was carried out as described herein at 400 psig in anice bath. After the reaction, the CO₂-hydrate temperature was between32.2 and 32.4° F., and 765 grams of Coke® syrup at 0° F. was pumped intothe reactor. The reactor was then stored in a −5° F. freezer at leastovernight (and up to two days over weekends). The reactor was opened andthe product was ground. The experiment was repeated four times todetermine repeatability and shelf life. Results are shown below. SampleDays after Carbonation No. Grinding Brix Level by weight 1 0 24.6 4.2% 121.2 2.6% 2 20.0 2.4% 3 21.4 2.3% 10 20.2 2.1% 2 0 22.2 4.8% 1 22.2 2.5%2 22.5 3.5% 9 25.8 2.4% 3 0 20.5 5.5% 1 21.0 2.8% 8 21.1 2.4% 4 0 24.94.9% 7 25.2 2.4%

Example 4

[0029] This experiment was conducted to determine optimal hydrationreaction time. A reactor was filled with 1.5 L of distilled water atroom temperature. The reactor was then purged three times with CO₂ at100 psig. The unpressurized reactor was then placed in an ice bath andagitated until the water temperature reached about 32.2° F. At thispoint carbon dioxide gas was introduced to the reactor at 400 psig. Thereaction was allowed to proceed with agitation, while continuing tointroduce CO₂ at 400 psig, for predetermined lengths of time, e.g., 5,10, 30, and 60 minutes. After the predetermined time for each reactiontime, the CO₂ was shut off to the reactor and the reactor was placed ina −5° F. room overnight. The next morning the reactor was depressurizedand opened and the level of carbonation measured. As a result of theseexperiments, it was determined that about 50% of the CO₂-hydrate hydratereaction takes place in the first five minutes of reaction time, about75% after 10 minutes, and almost 90% after 30 minutes. About 13% w/w CO₂was obtained after 60 minutes of reaction time. From this data, itappears that optimum reaction time for the CO₂ hydration reaction of thepresent invention should be between about 10 and 30 minutes.

[0030] While the preferred embodiment of this invention has beendescribed above in detail, it is to be understood that variations andmodifications can be made therein without departing from the spirit andscope of the present invention, as delineated by the following claims,including all equivalents thereof.

1. A method for preparing a frozen carbonated product comprising thesteps of: a) contacting CO₂ under pressure with an aqueous liquid in achilled reaction vessel; b) agitating said aqueous liquid and CO₂ insaid reaction vessel to promote a reaction between said CO₂ and aqueousliquid, thereby forming a CO₂-hydrate containing product; c) coolingsaid CO₂-hydrate containing product to promote freezing thereof; d)grinding said CO₂-hydrate containing product to form CO₂-hydratecontaining particles; and e) forming said CO₂-hydrate containingparticles into a frozen carbonated product.
 2. The method of claim 1wherein said aqueous liquid is chilled to greater than 32° F. but lessthan 32.2° F. prior to introducing said CO₂ and said CO₂ is introducedto said reaction vessel at a pressure of about 300-500 psig.
 3. Themethod of claim 1 wherein at the outset of said reaction, the aqueousliquid is at a temperature of about 32.1° F.
 4. The method of claim 1wherein said CO₂ under pressure and said aqueous liquid are reacted withagitation for about 5-60 minutes.
 5. The method of claim 1, wherein airis removed from said reaction vessel before reacting said CO₂ underpressure with said water.
 6. The method of claim 1, wherein followingthe forming of said frozen carbonated product, the temperature thereofis maintained sufficiently cold to maintain said product in a frozenstate.
 7. The method of claim 1, wherein steps a-d are conducted in aclosed system.
 8. The method of claim 1, wherein steps a-c are conductedin a closed system and steps d-e are conducted at atmospheric pressure.9. The method of claim 1, wherein a flavored syrup is added to saidCO₂-hydrate containing particles and mixed therewith, thereby forming aflavored frozen carbonated product.
 10. A method of preparing acarbonated ice product comprising the steps of: a) charging a reactorwith water, and subjecting said reactor charged with water to an inertgas purge; b) while agitating said water, cooling said water to atemperature slightly above its freezing point; c) charging said reactorwith CO₂ under pressure to provide a CO₂-water mixture; d) agitating theCO₂-water mixture while reacting said mixture to provide a productcomprising CO₂-hydrate; e) lowering the temperature of said product topromote freezing thereof; f) depressurizing said reactor; g) grindingsaid product to form a ground product; and h) dispensing said groundproduct.
 11. The method of claim 10, wherein a flavored syrup is addedto said product during grinding thereof, whereby said syrup becomesmixed therewith.
 12. The method of claim 11 wherein said flavored syrupis at the same or lower temperature as said ground product when mixedtherewith.
 13. The method of claim 10, wherein a flavored syrup is addedsubsequent to grinding said product, and is mixed therewith.
 14. Themethod of claim 10 wherein a flavored syrup is added prior to grindingsaid product.
 15. The method of claim 10, wherein said ground product ispackaged after dispensing, after a degassing step.
 16. The method ofclaim 15, wherein said ground product is stored at a home freezertemperature.
 17. The method of claim 16, wherein said home freezertemperature ranges from −10° F. to +5° F.
 18. The method of claim 10,wherein said ground product is compacted after grinding.
 19. The methodof claim 18, wherein said ground product is compacted in the form of anice pop together with a stick for holding the compacted ground product.20. The method of claim 10, wherein said ground product is dispensedinto a container for storage without compaction.
 21. The method of claim20, wherein said ground product is ground to achieve the consistency ofice cream.
 22. The method of claim 10, wherein said ground product isdispensed into a container for storage with compaction.
 23. The methodof claim 11, wherein said flavored syrup is sweetened with a naturalsweetener.
 24. The method of claim 11, wherein said flavored syrup issweetened with an artificial sweetener.
 25. The method of claim 10,wherein a cooled flavored syrup is added during grinding of saidproduct.
 26. The method of claim 10, wherein an artificially flavoredsyrup is added at one or more of steps a-g.
 27. The method of claim 10,wherein a naturally flavored syrup is added at one or more of steps e-g.28. The method of claim 10 wherein following reacting of said CO₂-watermixture to produce said product comprising CO₂-hydrate, said productcomprising CO₂-hydrate is stored at sub-freezing temperatures prior togrinding.
 29. The method of claim 28, wherein said product comprisingCO₂-hydrate is stored at about −5° F. for 0-48 hours prior to grinding.30. The method of claim 10, wherein said reaction proceeds for about5-60 minutes.
 31. The method of claim 10, wherein the agitation isprovided with a device selected from the group consisting of a stirrer,an ultrasonic device, and a shaker.
 32. The method of claim 10 whereinsaid water is chilled to 32.1° F. at the commencement of saidCO₂-hydrate reaction.
 33. The method of claim 10 wherein said inert gasused for said purge is CO₂.
 34. The method of claim 10 wherein saidproduct is ground to achieve a consistency resembling ice cream.
 35. Afrozen carbonated beverage that remains stable at home freezertemperatures, comprising a compacted mixture of frozen CO₂-hydrate andfrozen flavored syrup.
 36. The frozen carbonated beverage of claim 35,wherein said CO₂-hydrate comprises up to about 12% wt/wt CO₂ gas. 37.The frozen carbonated beverage of claim 35, wherein the frozen flavoredsyrup is artificially sweetened.
 38. The frozen carbonated beverage ofclaim 37 wherein said frozen carbonated beverage includes an emulsifier.39. The frozen carbonated beverage of claim 38 wherein said emulsifieris selected from the group consisting of pectin and guar gum.
 40. Amethod of preparing a carbonated ice confection product, comprising thesteps of: a) charging a reactor with water and purging the headspace ofsaid charged reactor with CO₂ gas; b) chilling said water in saidreactor to about 32.1° F., while providing agitation to said water; c)introducing CO₂ gas at a pressure of about 400 psig to said reactor, andagitating the water and CO₂ in said reactor, allowing an exothermicreaction of the water and CO₂ to proceed for about 30 minutes, therebyraising the temperature of the reactants to about 32.2-45° F., andthereby producing CO₂-hydrate; d) discontinuing the agitation andcooling the CO₂-hydrate to about −5° F. or less; e) slowlydepressurizing the reactor to about 5 psig or less; f) grinding theCO₂-hydrate; g) adding a flavored syrup to the ground CO₂-hydrate andmixing the syrup and CO₂-hydrate to produce the carbonated iceconfection product; h) compacting the carbonated ice confection product;and i) storing the carbonated ice confection product at a temperature ofless than about 5° F.